This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
The Digital Video Broadcasting-Terrestrial, noted DVB-T, is a standard for the transmission of digital terrestrial television. It is specified in the standard document ETSI EN 300 744: “Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for digital terrestrial television (DVB-T)”.
Within the digital terrestrial TV context, DVB-H is a DVB-T extension for broadcast services distribution to mobile terminals, also called handheld terminals. DVB-H mainly defines means for reducing power consumption and increasing reliability. It is specified in the standard document ETSI EN 302 304 V1.1.1 (2004 November) “Digital Video Broadcasting (DVB); Transmission System for Handheld Terminals (DVB-H)”. A difference brought by DVB-H over DVB-T is the fact that video and audio are transported in Internet Protocol packets, IP packets. The payload of DVB-H is constituted of IP datagram or other network layer datagram encapsulated into MultiProtocol Encapsulation sections. DVB-H introduces time-slicing in order to reduce the average power consumption of the terminal and to enable smooth and seamless frequency handover.
The time slicing technique is further described in ETSI standard, EN 301 192 V1.4.1 (2004 November) “Digital Video Broadcasting (DVB); DVB specification for data broadcasting”. With the time-slicing mechanism the sender sends a burst using the highest possible bit rate to multiple receivers. Time-slicing consists in sending data in bursts using higher instantaneous bit rate compared to the bit rate required if the data were transmitted using traditional streaming mechanisms. A burst comprises multiple sections. To indicate to the receiver when to expect the next burst, the time to the beginning of the next burst, which is the delta-t, is indicated in each section of the burst.
Time-slicing enables a receiver to stay active only a fraction of the time, while receiving bursts of a requested service. Between bursts belonging to the same service/stream, a DVB-H receiver may switch off its reception unit in order to save power. Once tuned to a TV service for instance, a terminal saves up to eighty percent of power as compared to a DVB-T tuner where the reception unit is continuously on. The set of time-sliced bursts is referred to a DVB-H channel hereinafter. Time slicing then enables a receiver to select a DVB-H channel for receiving a service, and not to listen to the other DVB-H channels.
Increasing reliability is done using a Forward Error Correction (FEC) mechanism. Each service, such as video service, is associated to one section whereas the service guide information, metadata, may be sent through a dedicated section. The device that transmits content using the time slicing and FEC techniques is called an IP Encapsulator (IPE).
The FIG. 1 represents a DVB-H distribution system, compliant with the ETSI TR 102 469 V1.1.1 (2006 May), “Digital Video Broadcasting (DVB); IP Datacast over DVB-H: Architecture”. It comprises a video content server 1 and a DVB-H IP Encapsulator (IPE) 2. The video content server is connected to the IPE in a manner well known to the skilled in the art of the DVB-H distribution system. The IPE sends the DVB-H content to the regional DVB-H transmission system 4 through the DVB-H distribution network 3. Only one IPE serves the entire network. The IPE is generally located in a national head-end office. Every DVB-H service is generated from this IPE including regional or local services.
An alternative DVB-H distribution system, not represented and described in the white paper “DVB-H Mobile TV flexible satellite distribution, UDcast, January 2007”, is based on several IPEs distributed over a set of regional areas. The same content, under the form of IP streams, is sent to all IPEs that generate DVB-H stream locally. This requires a unique management system to synchronize all IPEs together. All the IPEs distribute the same content locally.
These two architectures are not optimized. Either it requires sending all the content and services to the centralized IPE before being distributed. Or, with a regional distribution, it is very difficult to have a synchronized national network. In any case, it is not possible to modify the DVB-H stream once it has been generated at the IPE.